1. Technical Field
The present invention relates to a media processing device that conveys a recording medium having magnetic ink characters printed thereon through a media transportation path, and reads the magnetic ink characters and prints on the recording medium. The invention relates more particularly to a gap control method for a media processing device that can convey the recording medium without interference when reading magnetic ink characters, and to such a media processing device.
2. Related Art
Media processing devices that read magnetic ink characters printed on checks and print an endorsement on the checks are used for electronically processing checks. This type of media processing device is described in JP2001-283401A.
The media processing device taught in JP2001-283401A conveys checks or other recording media through a media transportation path passed a reading position and a printing position. The magnetic ink characters are read by a magnetic head by passing the recording medium at the reading position at a constant speed in contact with the magnetic head. After reading is completed, printing is done using a printhead at the printing position.
A small device size is desirable because the media processing devices used for check processing are installed at teller windows in banks, for example. As a result, the distance between the reading position and the printing position on the media transportation path is short, and the leading end of the recording medium reaches the printing position while the magnetic ink characters are still being read at the reading position. When the leading end of the recording medium reaches the printing position, the leading end of the recording medium may contact and catch on the printhead, thereby impeding media conveyance, because the gap between the printhead and the platen at the printing position is narrow. If conveyance of the recording medium is thus impeded while reading the magnetic ink characters, the recording medium will not pass the reading position at a constant speed, and magnetic ink character reading errors can easily occur.
The printing device taught in JP11-291572A has two flat surfaces formed at different angular positions on the outside surface of a cylindrical platen, and by rotating the platen sets one flat surface opposite the printhead to maintain a constant gap between the printhead and the platen for printing, and sets the other flat surface opposite the printhead to increase the gap between the platen and the printhead when the paper passes through.
JP08-11365A teaches a head gap adjustment mechanism that can adjust the gap between the printhead and cylindrical platen by eccentrically rotating the cylindrical platen.
Because the printing position of the printhead is determined by the platen, the recording medium is conveyed over the platen surface, and the gap between the printing surface of the recording medium and the printhead is thereby held constant. When the platen moves in the direction toward and away from the printhead, a step or gap is created between the platen and the upstream media guide that guides the recording medium to the platen. A step or gap also occurs between the platen and the downstream media guide that guides the recording medium downstream after passing the platen. As a result, smoothly conveying the recording medium by means of the platen may not be possible. It is therefore necessary to use a specially shaped cylindrical platen having flats on the outside surface as described in JP11-291572A so that a large step or gap is not created between the platen and the media guides on the upstream and downstream sides.